The last great necromancer has fallen, taking most of his knowledge with him and leaving behind two apprentices. Ceran values life and freedom, but the other desires power and control. He had seen the shift in the second's views, but couldn't bring himself to stop him, instead leaving behind a hidden repository of knowledge for only the kinder of the two.
Unfortunately, somehow the other gained awareness of this fact, and desired it for himself, leading to tragedy befalling many as they fell to become his undead horde. But perhaps undead puppets are not the best option, as Ceran thinks.